#include <sys/socket.h>
#include <stdlib.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
int create_socket(int network, char transport) {  

/* 'network' contains 4 for ipv4 or 6 for ipv6. 
   'transport' contains 'T' for TCP or 'U' for UDP. 
   The function returns -1 if the paramters do not match the above statement. */

	int domain;
	int type;

	if (network == 4) {
		domain = AF_INET;
	} else if (network == 6) {
		domain = AF_INET6;
	} else {
		return -1;
	}

	if (transport == 'T') {
		type = SOCK_STREAM;
	} else if (transport == 'U') {
		type = SOCK_DGRAM;
	} else {
		return -1;
	}

	int newSock = socket(domain,type,0);
	return newSock;
}


void create_addr(int network, char* address, int port,struct sockaddr* dest) {
/* Takes the relevant values - network (4 or 6), address, port - and fills them
   into dest */

	if (network == 4) {
		struct sockaddr_in listen_address;
		
		listen_address.sin_family = AF_INET;
		listen_address.sin_port = htons(port);
		inet_pton(AF_INET,address,&listen_address.sin_addr);
		memcpy(dest,&listen_address,sizeof(listen_address));
		return;	

	} else if (network == 6) {
		struct sockaddr_in6 listen_ipv6;
		listen_ipv6.sin6_family = AF_INET6;
		listen_ipv6.sin6_port = htons(port);
		inet_pton(AF_INET6,address,&listen_ipv6.sin6_addr);
		memcpy(dest,&listen_ipv6,sizeof(listen_ipv6));
		return;

	} else {
		exit(-2);
	}
		
}





int create_and_bind (int network, char transport, char* address, int port,struct sockaddr* addr_struct) {
/* combines the socket creation and address creation into one
   function - simply pass the required values, and a structure,
   and this function does the legwork for you */

	int socket = create_socket(network,transport);
	if (socket == -1) {
		exit(-1);
	}
	create_addr(network,address,port,addr_struct);
	int addrlen = sizeof(*addr_struct);
	int i = bind (socket,addr_struct,(socklen_t)addrlen);
	if (i < 0) {
		exit(-3);
	}
	return socket;
}

int create_remote (int network,char transport,char* address,int port) {
/* same as 'create_and_bind', but for remote sockets - client rather
   than server sockets */

	int socket = create_socket(network,transport);
	if (socket == -1) {
                exit(-1);
        }
	struct sockaddr remote_addr_struct;
        create_addr(network,address,port,&remote_addr_struct);
        int addrlen = sizeof(remote_addr_struct);
        int i = connect(socket,&remote_addr_struct,(socklen_t)addrlen);
	if (i < 0) {
		printf("Something went wrong: %s\n",strerror(errno));
		exit(-3);
	}
        return socket;
}

void forward_data(int from_fd, int to_fd) {
	int n = 0;
        char* buffer = malloc(3000*sizeof(char));
	while ((n = recv(to_fd, buffer, 3000, 0)) > 0) { // read data from input socket
        	send(to_fd, buffer, n, 0); // send data to output socket
	}
}

int main() {

	int preferred_network = 4;
	char preferred_transport = 'T';
	struct sockaddr addr_struct;
	int server_sock = create_and_bind(preferred_network,preferred_transport,"127.0.0.1",3000,&addr_struct);
	int addrlen = sizeof(addr_struct);

	listen(server_sock,50);  /* Arbitrary number, change later */

	while (1) {
	int from_client = accept(server_sock,&addr_struct,(socklen_t *)&addrlen);	
	int to_server = create_remote(preferred_network,preferred_transport,"127.0.0.1",5000);
	
	if (fork() == 0) {

	/* fork returns 0 for a child, so we're in the child's execution
	   right now */
		close(server_sock);
		if (fork() == 0) {
			forward_data(from_client,to_server);
			exit(0);
		}
		if (fork() == 0) {
			forward_data(to_server,from_client);
			exit(0);
		}
		exit(0);


	}
//	recv(from_client,buffer,3000,0);
			

//	printf("%s",buffer);
	

	}

}